Preparation of alicyclic amines from alicyclic isothiocyanates



United States Patent 3 150,183 PREPARATION OF ALICYCHC AMINES FRGMALICYELIC ISOTHIOCYANATE George A. Buntin, Vlilmington, DeL, assignor toHercules Powder Company, Wilmington, Del, a corporation of Delaware NoDrawing. Filed Jan. 5, 1962, Ser. No. M45616 7 Claims. (Cl. 260-563)This invention relates to the conversion of an organic isothiocyanate toan organic amine.

Methods of conversion of an organic-isothiocyanate to an amine by acidhydrolysis and by alkaline hydrolysis are known.

In accordance with the present invention it has now been found thatimproved yields of amine are obtained by reacting an organicisothiocyanate with elementary chlorine and water.

The process of this invention is generally applicable for conversion ofan organic isothiocyanate of the general formula RSCN to an amine of theformula RNH where R is an organic radical.

The process of this invention is illustrated by the following exampleswherein all parts and percentages are by Weight.

Example 1 2-norbornylisothiocyanate was prepared by adding parts 75%sulfuric acid dropwise over a two-hour period with stirring to asuspension of 28.2 parts norbornylene and 29.1 parts crushed potassiumthiocyanate in 130 parts toluene at 40 C. and continuing stirring for anadditional 3 hours. This resulted in the formation of HSCN in situ andthe addition thereof to the double bond of the norbornylene. The organiclayer was separated and 2- norbornylisothiocyanate boiling at 7480C./0.3 mm. recovered therefrom.

To 30 parts of 2-norbornylisothiocyanate in 200 parts of glacial aceticacid containing 4 parts water at 20-30 C. was added 28 parts of chlorinegas with stirring over a 30-minute period. The acetic acid was distilledoff at reduced pressure up to a pot temperature of 50 C. at 30 mm. Thewhite solid residue was diluted with hexane, filtered ofi, washed withhexane, and dried. Twenty-six parts of white crystalline powder wasobtained. It analyzed 9.6% N and 22.8% C1 compared to the calculatedvalues of 9.5% N and 24.1% 01 for norbornylammonium chloride. To 250parts of water at 60 C. was added 24.5 parts of norbornylamrnoniumchloride. The resulting solution was filtered to remove 0.3 part ofbrown, insoluble material. The filtrate was made basic with NaOH, andextracted twice with 160 parts each of benzene. The benzene extractswere combined, dried over Na SO and distilled. Twelve parts ofwater-white liquid was collected at 5556 C. at 25 mm. pressure. It had aneutral equivalent of 111.9 compared to a calculated value of 111.5 forZ-norbornylamine. Another preparation distilled at 5355 (1/18 mm. andhad a refractive index N =l.4849.

Example 2 Example 3 Cyclopentadiene was reacted with butene-Z in theDiels Alder reaction to produce 5,6-dimethylnorbornylene, and this wasreacted with HSCN as in Example 1. The resulting 2 (5,6dimethylnorbornyl)isothiocyanate was treated with chlorine as inExample 1. The amine produced was 2-(5,6-dimethylnorbornyl)amine, B.P.76- 78/16 mm, N =1.4865.

Example 4 Cyclopentadiene was reacted with pentene-l in the Dials-Alderreaction to produce propylnorbornylene, and this was reacted with HSCNas in Example 1. The re sulting Z-(propylnorbornyl)isothiocyanate wastreated with chlorine as in Example 1. The amine produced wasZ-(propylnorbornyl)amine B.P. 38-40" C./O.25 mm.

Example 5 Cyclopentadiene was reacted with butene-l in the Diels- Alderreaction to produce ethylnoroornylene, and this was reacted with HSCN asin Example 1, and the resulting 2- (ethyinorbornyl)isothiocyanate wastreated with chlorine as in Example 1. The amine produced wasZ-(ethylnorbornyl) amine, 3.1 3840 C./0.8 mm, N =1.4792.

Example 6 Cyclopentadiene was reacted with allyl chloride in theDials-Alder reaction to produce chloromethylnorbornylone, and this wasreacted with HSCN as in Example 1. The resulting2-(chlorornethylnorbornyl)isothiocyanate was treated with chlorine as inExample 1, and the resulting amine salt was converted to the free amine.The 2- (chloromethylbornyl)amine obtained was distilled at 64 68 C./0.25mm, refractive index N =1.5l12.

Example 7 Cyclopentadiene condensed with vinyl chloride in theDiels-Alder reaction formed chioronorbornylene which was reacted withHSCN as in Example 1, and the resulting chloronorbornyl-2-isothiocyanatewas treated with chlorine as in Example 1, and the resulting amine saltwas converted to the free amine. The Z-(chloronorbornyD- amine obtainedwas distilled at 68 C./0.5 mm.

Example 8 Tetrahydrodicyclopentadienylisothiocyanate was chlorinated asin Example 1 in acetic acid containing a small amount of water.Tetrahydrodicyclopentadienylamine was recovered from the hydrochlorideproduced in this reaction. It was a water-White liquid, B.P. 8486/ 1mm., N =1.5l78.

The process of this invention, when applied to organic isothiocyanatesof the formula RSCN, where R is any organic radical carrying nointerfering functional groups, produces the corresponding amine RNH Byway of further examples, the following isothiocyanates produce thecorresponding amines:

Cyclohexylisothiocyanate yields cyclohexylarninep-menthanylisothiocyanate yields p-menthanylamineDichloronorbornylisothiocyanate yields dichloronorbornylarnine Theorganic radicals which carry no interfering functional groups are cyclicalkyl groups and their halogen, amino, nitro, hydroxyl, ether, keto, andcarboxyl substitution products. Interfering functional groups which are'absent are ethylenic double bonds, acetylenic triple bonds, aryl groupsand mercapto groups.

The process of this invention appears to involve two main reactions asfollows:

and these reactions may be carried out stepwise by first chlorinating'inthe absence of water and then hydrolyzing by reaction with water, orboth reactions may be carried out simultaneously. Unless a completelyanhydrous systern is used in the chlorination, the second reaction willtake place to the extent that there is suihcient water present. Whenglacial acetic acid is used as a solvent in complete absence of water,it is possible that there is an intermediate reaction in which aceticacid adds to RNCCI forming, for example,

which on subsequent addition of water hydrolyzes to the amine,hydrochloric acid, carbon dioxide and acetic acid. When carbontetrachloride is used for the chlori-" nation solvent, the compoundRNCCl can be isolated by distilling off the by-product SO1 and carbontetrachloride. The hydrolysis step can be carried out as a subsequentstep by contacting this intermediate with water in the chlorinationsolvent or in a different solvent or in the absence of a solvent. Themechanism of the reaction is not important, however, except for makingobvious variations in which reaction takes place with chlorine andsubsequently with water whether water is present during the chlorineaddition or is added after the intermediate chlorination product isformed.

The amount of chlorine and water required for the reaction is, asexpressed in the above equations, two moles each of chlorine and waterfor each NCS group present. An excess of either may be used, but onlythe theoretical amount reacts in the process of this invention.

The process of chlorination may be carried out in water or dilutehydrochloric acidas, for instance, in chlorine water or Javelle water,or in water-free or watercontaining organic solvents such as aceticacid, chloroform, carbon tetrachloride, ethyl chloride, ethylenechloride, methylene chloride, hexane, benzene, toluene and xylene. Ingeneral, the volatile organic acids, aliphatic hydrocarbons, aliphaticchlorohydrocarbons, cyclo-paraffins, and aromatic hydrocarbons areparticularly suitable. The same solvents are useful in the hydrolysisstep. \Vhere both chlorination and hydrolysis are carried outsimultaneously, it is preferable to use a lower fatty acid such asacetic acid which is a solvent for both the organic reagent and thewater.

The reaction of the organic isothiocyanate with chlorine is carried outby contacting the organic isothiocyanate with elementary chlorine at atem erature above -50 C. and below that at which the desired amine isdestroyed. The preferred temperature for an anhydrous system, or whenwater is present, is to 50 C., but temperatures as highas 100 C. and aslow as 5() C. are

. operable.

The amine salt may be recovered in many ways other than by distillingoff the solvent, as will be obvious, and is not limited to distillation.The salt may be rendered insoluble, for example, by addition of propane,or hex- 4i ane, and separated by filtration, and the propane may then bedistilled oil so that the mother liquor can be reused.

The free amine can be separated from the amine hydrochloride bytreatment with alkalies or by ion exchange resins. In some cases wherethe amine is steam volatile, it can be steam distilled from an aqueousalkaline solution. An alkali or alkaline earth hydroxide or carbonatemay be used to neutralize the hydrochloric acid so as to liberate thefree amine. These methods are well known in the art of liberating freeamine from amine hydrochlorides.

The process of this invention is particularly desirable for thepreparation of amines not readily produced by other methods. Theisothiocyanates used as reagents are readily produced in many instancesby the addition of HSCN, produced in situ, to the unsaturatedcompoundcorresponding to the desired organic radical. This is aparticularly useful method for producing amines in which the organicradical is a norbornyl ring having an amine group in the 2-position onthe norbornyl ring. A variety of such amines is produced by reactingcyclopentadiene with substituted and unsubstituted hydrocarbons having.

one double bond to produce compounds having the norbornylene ring,adding HSCN to these norbornylene compounds to form the isothiocyanate,and then treating the resulting organic isothiocyanate with chlorine andwater.

This application is a continuation-in-part of application Serial No.75,917, filed December 15, 1960, which in turn is a continuation-in-partof application Serial No. 5,670, filed February 1, 1960, and nowabandoned, by George A. Buntin and William R. Diveley.

What I claim and desire to protect by Letters Patent is:

1. The method of preparing an amine of the formula RNH where R is analicyclic organic radical selected from the group consisting of thesaturated hydrocarbon radicals and chlorohydrocarbon radicals whichcomprises contacting an alicyclic organic isothiocyanate with elementarychlorine and water at a temperature in the range of 0 C to C. until RNH-HC1 is formed and separating RNH therefrom.

2. The method of claim 1 in which Risthe norbornyl radical.

3. The method of claim 1 in which R is the chloromethylnorbornylradical.

4. The method of claim 1 in which R is the chloronorbornyl radical.

5. The method of claim 1 in which R is the methylnorbornyl radical.

6. The method of claim 1 in which R is the dimethylnorbornyl radical.

7. The method of claim 1 in which R is the p-rnenthanyl radical.

References tfited in the file of this patent Sell: Ber. Dent. Chem, vol.7, pp. 12281234 (1874) QDlD l.

1. THE METHOD OF PREPARING AN AMNE OF THE FORMULA RNH2, WHERE R IS ANALICYCLIC ORGANIC RADICAL SELECTED FROM THE GROUP CONSISTING OF THESATURATED HYDROCARBON RADICALS AND CHLOROHYDROCARBON RADICALS WHICHCOMPRISES CONTACTING AN ALICYCLIC ORGANIC ISOTHIOCYANATE WITH ELEMENTARYCHLORINE AND WATER AT A TEMPERATURE IN THE RANGE OF 0*C. TO 100*C. UNTILRNH2-HCL IS FORMED AND SEPARATING RNH2 THEREFROM.